It is understood in the art that spherical fittings may be utilized advantageously in pipelines and tubular structures to reduce stress concentrations in the joints between pipe sections or structural members. Spherical fittings are ideally configured for uniformly distributing loads and stresses throughout the joint.
However, spherical fittings have not found wide spread application in the industry primarily because of the fact that they are relatively expensive to fabricate, and in addition, conventional spherical fittings may themselves introduce areas of stress concentration in the joint. In this later regard, spherical fittings typically comprise a hollow spherical body on which radially extending outlets are welded to permit intercoupling with pipes in the system. In the case of a tubular trusswork, the structural members themselves may be shaped to mate with the outer surface of the spherical body for welding thereon such that the need for radially extending outlets is obviated. In either instance, welding at the high stress area immediately adjacent the spherical surface of the fitting body may introduce sources of stress concentration and crack initiators if not performed properly. This problem is compounded by the fact that construction of tubular trussworks and pipelines is often times performed in areas where nondestructive testing of the welded joint is virtually impossible.